Field of the Invention
The present invention relates to correction of a position correction of an image formed on a sheet.
Description of the Related Art
When an image is formed by an image forming apparatus, there are cases in which a formation position of the image is misaligned from an ideal position on a sheet. According to Japanese Patent Laid-Open No. 2003-173109, causing a sheet on which a reference image is formed to be read by a reading apparatus, and obtaining a distance from an end of the sheet to the reference image based on the read result to adjust the image formation position based on that distance is proposed.
Note that there are various reasons for an image formation position being misaligned from an ideal position on a sheet. For example, sometimes this is caused by a conveyance mechanism or a position misalignment due to a size or a grammage of a sheet. In any case, an amount of misalignment of an image formation position is established by reading a reference image formed on a sheet. An image forming apparatus forms an image at an ideal position on a sheet by correcting in advance the formation position of an image in accordance with such an amount of misalignment. However, an image formation position ceases to be correctly corrected when there is a read error caused by an individual difference in a reading apparatus. For example, there are reading apparatuses that employ a wire winding drive for wide scanning such as for an A3 size sheet. The carriage moves in a state in which it is slightly tilted with respect to a scan direction due to bending of a rail or eccentricity of a pulley used in a wire winding drive. As a result, a read error occurs due to the scan image also being tilted, and the image formation position correction precision is reduced.